For example, a mask blank, which is a raw material of a mask (reticule) used for a photolithography method, has a structure in which various kinds of thin films such as a light-shielding film, which is also referred to as an opaque film, and a phase shift film optically relating to a transfer exposure light are formed on a substrate surface, and further, a resist film is formed on an uppermost layer of each kind of the thin film, or an antireflection film and a conductive film are formed on or under the resist film, and further a protective film, etc., for protecting the thin films is formed.
A specific example of this mask blank includes a mask blank having resist, whose uppermost layer is a resist film. The mask blank having resist is formed in such a manner that each kind of thin film is formed on the substrate surface, and thereafter, the resist film is coated thereon by a method such as a spin-coating method, and further a prescribed heating and drying process (including a cooling process), etc., is applied.
Note that the thin film formed on the substrate surface includes the light-shielding film, the phase shift film (in a case of phase shift mask), a reflecting film and an absorbing film (in a case of X-ray mask), or the antireflection film, etc. The above-described thin films have some sort of relation with the transfer exposure light in such a way as to allow the transfer exposure light to pass or inhibit the exposure light from passing, and function to form a prescribed transfer pattern image on a transfer target.
FIG. 2 is a sectional view of the conventional mask blank having resist. As shown in FIG. 2, the mask blank 10 having resist is formed by sequentially forming a light-shielding film 2 and an antireflection film 3 on a substrate 1 such as a glass, etc., and coating thereon a resist film 4 by the spin-coating method, etc. However, in many cases, unnecessary build-up parts 4a are generated in the peripheral edge of the substrate 1 (specifically, a part along four sides of the main surface of the substrate 1), and also an unnecessary side face resist 4b is formed on the side face of the substrate 1.
Meanwhile, generally, the mask blank 10 having resist is contained in a storage container during transporting and storing it. FIG. 3 is a perspective view of an inner box 20 of a storage container 50 for containing plural sheets of mask blanks 10 having resists, and FIG. 4 is a sectional view of the storage container 50.
The storage container 50 includes an outer box 30 and the inner box 20, with the inner box 20 contained and fixed in the outer box 30. The inner box 20 is contained and fixed so that a plurality of grooves 21 are provided on a pair of side wall parts of the container which is a rectangular shape with an upper opening and facing each other, and two sides 10a and 10b of the mask blank 10 having resist are inserted into the grooves 21.
However, as described above, the unnecessary build-up parts 4a and the unnecessary side face resists 4b are formed on two sides 10a and 10b of the mask blank 10 having resist. Therefore, when the mask blank 10 having resist is contained and/or taken in/out of the inner box 20, the unnecessary build-up parts 4a and the unnecessary side face resists 4b are made to touch and rub the grooves 21, etc., of the inner box 20. In addition, a vibration or a shock may be occurred in some cases, caused by moving and transporting it with the mask blank 10 having resist retained by the grooves.
In another case, the unnecessary build-up parts 4a and the unnecessary side face resists 4b may also touch and rub the grooves 21 of the inner box 20 by the vibration and the shock. As a result, the unnecessary build-up parts 4a and the unnecessary side face resists 4b are easily peeled off/fallen off from the substrate 1 to become dust/dirt, which adheres to the mask blank itself or each kind of processing device. This finally causes a defect of the mask (including reticule), which is a product made from the mask blank as a raw material, or causes the possibility of a low yield of the mask.
In order to solve the above-described problems, as a technique to remove the unnecessary resist film formed on the peripheral edge of the substrate 1, a method for selectively removing the unnecessary resist film of the peripheral edge of the substrate after coating resist has been generally used (For example, see patent document 1, patent document 2, and patent document 3).
(Patent Document 1)
Japanese Patent publication No. 57-13863
(Patent Document 2)
Japanese Patent Laid Open No. 63-160332
(Patent Document 3)
Japanese Patent Laid Open No. 2001-259502